Process for preparing physically stable crystalline gamma modification of para-aminobenzenesulfonamide

ABSTRACT

A process for preparing a physically stable crystalline γ-modification of para-aminobenzenesulfonamide comprises cooling a para-aminobenzenesulfonamide solution in water or an organic solvent at rate of at least 2° C./min to complete crystallization thereof and subsequently separating the resulting crystals and drying thereof.

This is a U.S. national stage application under 35 U.S.C. §371 basedupon PCT International Application No. PCT/RU93/0024, filed on Nov. 16,1993.

This is a U.S. national stage application under 35 U.S.C. §371 basedupon PCT International Application No. PCT/RU93/0024, filed on Nov. 16,1993.

FIELD OF ENGINEERING

The present invention relates to organic chemistry, more particularly toa process for preparing a physically stable crystalline γ-modificationof para-aminobenzenesulfonamide.

PRIOR ART

It is well known that para-aminobenzenesulfonamide may crystalline atleast in three polymorphous modifications designed as α-, β- and γforms(Journal of Pharmaceutical Sciences, v. 59, No. 7, July 1970, p.972-975; Journal of Pharmaceutical of Japan, 1942, v. 63, No. 11, p.17-19) from which only the α-form is being used in medical practice.Said polymorphous modifications can be prepared by crystallization andconversion of one form into the other.

The crystalline γ-modification of para-aminobenzenesulfonamide can beprepared by dissolving in amyl alcohol of β-modification followed byboiling. The resulting crystals are thermally insulated, graduallycooled to room temperature and filtered. The γ-modification isidentified by a radiographic analysis method.

Also known in the art is a process for preparing the γ-modification ofpara-aminobenzenesulfonamide by pulverization of α- and β-modificationsand subsequently heating the resulting powder at 130°-140° C. for 1hour. In this case, the β-modification is converted into theγ-modification. However, the γ-modification ofpara-aminobenzenesulfonamide prepared by the processes indicted above isunstable at room temperature and is converted into the β-modificationwhich is then spontaneously converted into the γ-modification. Since theresulting γ-modification is unstable, its pharmacological activity hasnot been investigated. Said processes for preparing the γ-modificationof para-aminobenzenesulfonamide have not been used on an industrialscale.

DISCLOSURE

The object of the invention is to provide a process by changing thetechnological operations which would make it possible to obtain aphysically stable crystalline γ-modification ofpara-aminobenzenesulfonamide having high antimicrobial andinterferon-inducing

The problem can be solved in that in the claimed process for preparing aphysically stable crystalline γ-modification ofpara-aminobenzenesulfonamide having, a solution ofpara-aminobenzenesulfonamide in water or an organic solvent or in amixture thereof is cooled with a cooling agent at a rate of not lowerthan 2° C./min to complete crystallization thereof followed byseparation of resulting crystals and drying thereof.

It is desirable to use lower alcohols, preferably ethanol, as organicsolvent. To increase the yield of the desired product, it is desirableto use liquid nitrogen or liquid carbon dioxide as the cooling agent,and to carry out the drying operation by vaccum treatment at a pressurenot higher than 10⁻² mm Hg. The claimed process makes it possible toobtain a physically stable crystalline γ-modification ofpara-aminobenzenesulfonamide which is stable during storage at roomtemperature and has antimicrobial activity higher than the activity ofthe β- and α-forms used in medical practice and also has a highlyeffective interferon-inducing activity. The claimed process ischaracterized by simply technology and suitable for industrial use.

BETTER EMBODIMENT OF THE INVENTION

The claimed process for preparing a physically stable crystallineγ-modification of para-aminobenzenesulfonamide is carried out by coolinga solution of para-aminobenzenesulfonamide in water or an organicsolvent or in a mixture thereof with a cooling agent at a rate of atleast 2° C./min to complete crystallization thereof followed byseparation of the resulting crystals and drying thereof. The coolingagent may be any substance capable of reducing the temperature of thesubstance to be cooled at a rate of at least 2° C./min. The opticalsubstance used as the cooling agent is liquid nitrogen or liquid carbondioxide, the use of these substances increases the yield of the desiredproduct by quickly establishing and further maintaining the requiredcooling rate.

A physically stable crystalline γ-modification of said compound can beprepared at a cooling rate of least 2° C./min. The process carried outat a cooling rate of lower than 2° C./min does not make it possible toobtain new crystalline modification. The upper cooling rate is notrestricted. At any maxim highest attainable cooling rate of the startingsolution, a new crystalline modification is formed. The cooling processis carried out in water or in any organic solvent or in a mixturethereof in which the starting substance is soluble. Preferred solventsare water and lower alcohols, preferably ethanol. In this case, thehighest yield of the desired product attained. The claimed substance canbe obtained irrespective of the concentration of the starting substancein solution. The drying conditions at pressure higher 10⁻² mm Hg arechosen because the final dried product should have a moisture content ofnot higher than 3%. The resulting desired product is a physically stablecrystalline γ-modification of para-aminobenzenesulfonamide represents awhite fine powder (crystals of elbow form typical of theγ-modification). The analysis of the spectra and X-ray diagrams confirmsthe fact that the resulting desired product is γ-modification of saidcompound and is defined by the following values of interplane distancesd and reflex relative intensities I:

    ______________________________________                                                d, A I                                                                ______________________________________                                                7.63 31                                                                       6.61 73                                                                       6.28 8                                                                        6.00 3                                                                        5.64 30                                                                       4.90 71                                                                       4.51 100                                                                      4.27 4                                                                        4.19 5                                                                        3.80 98                                                                       3.66 30                                                                       3.56 32                                                                       3.47 4                                                                        3.36 4                                                                        3.23 8                                                                        3.20 12                                                                       3.13 13                                                                       3.04 30                                                                       2.99 25                                                                       2.81 13                                                                       2.67 2                                                                        2.64 3                                                                        2.62 2                                                                        2.53 5                                                                        2.49 10                                                                       2.46 6                                                                        2.33 9                                                                        2.25 6                                                                        2.22 4                                                                        2.21 4                                                                        2.17 4                                                                        2.16 4                                                                        2.14 4                                                                        2.12 8                                                                        2.11 9                                                                        1.99 5                                                                        1.97 6                                                                        1.93 4                                                                        1.92 5                                                                        1.91 5                                                                        1.88 5                                                                        1.86 4                                                                        1.84 3                                                                        1.82 4                                                                        1.80 5                                                                        1.77 3                                                                        1.75 3                                                                        1.727                                                                              5                                                                        1.618                                                                              4                                                                        1.583                                                                              3                                                                        1.566                                                                              4                                                                ______________________________________                                    

The resulting physically stable crystalline γ-modification ofpara-aminobenzenesulfonamide has an antimicrobial andinterferon-inducing activity.

The activity of the resulting γ-modification was investigated inexperiments on amimals as compared with pharmacopeanpara-aminobenzenesulfonamide (comprising substantially theα-modification) used in medical practice.

In order to investigate -he specific antimicrobial activity, a method ofserial dilutions was used. The starting solutions were 0.5% solutions ofpharmacopean para-aminobenzenesulfonamide and the γ-modification of saidcompound in a 0.1 N sodium hydroxide solution.

Two-fold dilutions of the test solutions were prepared in a meatpeptonic broth with the addition of Staphylococcus aureas. The seedswere kept in a thermostat for 24 hours. The bacteriostatic concentrationwas determined visually. Sterile and non-sterile solutions ofpara-aminobenzenesulfonamide and of the γ-modification were used.

The experiments were carried out in three series of the test solutionson three-fold dilutions.

The results are presented in Table 1. The analysis of the data presentedin Table 1 is indicative of the fact that the γ-modification hasantimicrobial activity which is not inferior to the activity of thepharmacopean para-aminobenzenesulfonamide.

                                      TABLE 1                                     __________________________________________________________________________                 Time, days Growth (visually)                                     Nos                                                                              Test agent                                                                              0     1     2     3      Control                                 1  2         3     4     5     6      7                                       __________________________________________________________________________    1  Sterile solvent                                                                         No growth                                                                           Growth                                                                              Growth                                                                              Growth Growth                                  2  Pharmacopean                                                                            No growth                                                                           No growth                                                                           No growth                                                                           Growth Growth                                     para-aminoben-                                                                zenesulfonamide                                                            3  γ-modification                                                                    No growth                                                                           No growth                                                                           No growth                                                                           Growth Growth                                     of para-aminoben-                                                             zenesulfonamide                                                            4  Non-sterile                                                                             No Growth                                                                           Growth                                                                              Growth                                                                              Growth Growth                                     solvent                                                                    5  Pharmacopean                                                                            No growth                                                                           No growth                                                                           No growth                                                                           Growth Growth                                     para-aminoben-                                                                zenesulfonamide                                                               (non-sterile agent)                                                        6  γ-modification                                                                    No growth                                                                           No growth                                                                           No growth                                                                           Growth Growth                                     of para-aminoben-                                                             zenesulfonamide                                                               (non-sterile agent)                                                        __________________________________________________________________________

The investigation of the toxic effects of the γ-modification ofpara-aminobenzensulfonamide as compared with pharmacopeanpara-aminobenzenesulfonamide showed that the γ-modification has lowertoxicity, namely, LD₅₀ is 1918 m%/kg of animal body when administeredintraperitoneally, whereas LD₅₀ of the pharmacopean agent is 1242 mg/kgof animal body. The interferon-inducing activity of he γ-modification ofpara-aminobenzenesulfonamide was compared with that of pharmacopeanpara-aminobenzenesulfonamide on mice in vivo experiments.

The experiments used CBA strain male rats weighing 10-12 g and Z-929mouse fibro-blast intertwine cell strain. The cells were grown inplastic 96-hole plates (37° C., 3.5% CO) in medium Needle 2 HEM of 10%cattle serum. The mouse encephalocardite virus (the Columbia strain) waschosen as a virus.

The pharmacopean agent and the γ-modification ofpara-aminobenzenesulfonamide were administered singly intraperitoneally(0.2 ml per mouse) at 50 and 150 mkg/0.2 ml doses. The blood was takenfrom the carotid 5, 24 and 72 hours after administration of the agents.At least 5 animals were used for each sample. The interferon titrationwas carried out by determining the suppression of a cytopathic effect onthe cell culture by using a micromethod.

The investigation results are presented in Table 2.

                  TABLE 2                                                         ______________________________________                                        Dynamics of Interferon Formation of the Mouse                                 Blood Serum during Administration of Test Agents                                                 Interferon titers                                                     Blood/time                                                                            (units/ml)                                                                  after ad- Agent con-                                                                             Agent con-                                                 ministra- centration,                                                                            centration,                                                tion of   50 mkg/mo-                                                                             150 mkg/mo-                               Nos  Agent       agent, Hr use      use                                       1    2           3         4        5                                         ______________________________________                                        1    Pharmacopean                                                                               5        <20      <20                                            para-       24        <20      <20                                            aminobenzene-                                                                             72        <20      <20                                            sulfonamide                                                              2    γ-modification                                                                       5        40-80     80                                            of para-    24        160      320                                            aminobenzene-                                                                             72        <20      <20                                            sulfonamide                                                              3    Control      5        <20                                                                 24        <20                                                                 72        <20                                                4    Mouse serum --        640                                                     interferon                                                               ______________________________________                                    

The analysis of the investigation results showed that pharmacopeanpara-aminobenzenesulfonamide has no inter-feron-inducing activity. Atthe same time the γ-modification of this agent induced interferon in themouse blood serum as early a 5 hours after administration (earlyinterferon) with an activity of 40-80 units/ml, and after 24 hours theinterferon titers were as high as 160-320 units/ml. By the end of 72hours the interferon titers became lower. Thus the crystallineγ-modification of para-aminobenzenesulfonamide obtained by the claimedprocess is physically stable form having a highly effectiveantimicrobial and interferon-inducing activity. In order to betterunderstand the present invention, the following examples are provided onthe preparation of a physically stable crystalline γ-modification ofpara-aminobenzenesulfonamide.

EXAMPLE 1

1.5 l of an aqueous solution of para-aminobenzenesulfonamide having aconcentration of 20 g/l are cooled with liquid nitrogen at a coolingrate of 2° C./min to complete crystallization thereof. The resultingfrozen mass is transferred to trays and placed into subliminator. Thedrying operation is carried out at a pressure of 10⁻² mm Hg to aresidual moisture content of 3%. The yield of the desired product is30%(100%). The resulting product is a white fine crystalline powder. Theresulting substance is characterized by the values of interplanardistances d and relative reflexes I identical with the correspondingvalues of the crystslline γ-modification of para-aminobenzenesulfonamidegiven above.

EXAMPLE 2

The process is carried out as described in Example 1. In this case, 500ml of a solution of the starting agent are used in a water/ethanol (1:1) mixture having a concentration of 20 g/l . The yield of the desiredproduct is 96 wt %. The resulting agent ha characteristics similar tothose described in Example 1.

EXAMPLE 3

The process is carried out as described in Example 1 at a cooling rateof 30° C./min. The yield of the desired product is 98.2 wt %. Theresulting product has characteristics similar to those in Example 1.

EXAMPLE 4

1.5 1 of a para-aminobenzenesulfonamide solution in ethanol having aconcentration of 10 g/l are cooled with liquid nitrogen at a coolingrate of 8° C./min to complete crystallization of the solution. Theresulting frozen mass is placed into a sublimator. The drying operationis carried out at a pressure of 10⁻² mm Hg. The yield of the desiredproduct is 95.6 wt %. The resulting compound has characteristics similarto those in Example 1.

EXAMPLE 5

The process is carried out as described in Example 1. The concentrationof the starling compound in ethanol 10 g/l, and the cooling agent isliquid carbon didoxide.

The yield of the desired product is 96.8 wt %. The resulting compoundhas characteristics similar to those in Example 1.

INDUSTRIAL APPLICABILITY

The physically stable crystalline γ-modification obtained by the claimedprocess has highly effective antimicrobial and interferon-inducingactivity and find applications in medical practice as the activeingredient of the drug.

I claim:
 1. A process for preparing a physically stable crystalline gamma modification of para-aminobenzenesulfonamide, the process comprising the steps of:(a) providing a solution of para-aminobenzenesulfonamide in water, in an organic solvent, or in a mixture of water and organic solvent; (b) cooling the solution with a cooling agent at a rate of at least 2° C./min to form crystals of the gamma modification of para-aminobenzenesulfonamide; and (c) separating and drying the crystals formed in step (b).
 2. A process according to claim 1, wherein the organic solvent comprises a lower alcohol.
 3. A process according to claim 2, wherein the lower alcohol is ethanol.
 4. A process according to claim 1, wherein the cooling agent is liquid nitrogen or liquid carbon dioxide, and the drying is carried out by vacuum treatment at a pressure not higher than 10⁻² mm Hg.
 5. A process according to claim 2, wherein the cooling agent is liquid nitrogen or liquid carbon dioxide, and the drying is carried out by vacuum treatment at a pressure not higher than 10⁻² mm Hg.
 6. A physically stable crystalline gamma modification of para-aminobenzenesulfonamide prepared by a process comprising:a) cooling using a cooling agent a solution of para-aminobenzenesulfonamide at a rate of at least 2° C./min to form crystals of the gamma modification of para-aminobenzenesulfonamide; and b) separating and drying the crystals formed in step a).
 7. The physically stable crystalline modification of para-aminobenzenesulfonamide prepared according to claim 6, wherein the para-aminobenzenesulfonamide solution is para-aminobenzenesulfonamide in water, an organic solvent or a mixture thereof.
 8. The physically stable crystalline modification of para-aminobenzenesulfonamide prepared according to claim 7, wherein the organic solvent is a lower alcohol.
 9. The physically stable crystalline modification of para-aminobenzenesulfonamide prepared according to claim 7, wherein the organic solvent is ethanol.
 10. The physically stable crystalline modification of para-aminobenzenesulfonamide prepared according to claim 6, wherein the cooling agent is liquid nitrogen or liquid carbon dioxide.
 11. The physically stable crystalline modification of para-aminobenzenesulfonamide prepared according to claim 6, wherein the drying is carried out by vacuum treatment at a pressure not higher than 10⁻² mm Hg.
 12. A process according to claim 3, wherein the cooling agent is liquid nitrogen or liquid carbon dioxide, and the drying is carried out by vacuum treatment at a pressure not higher than 10⁻² mm Hg. 